This invention relates to the production of 2,2',4,4',6,6'-hexanitrostilbene.
2,2',4,4',6,6'-hexanitrostilbene (HNS) is a well known thermally stable explosive. U.S. Pat. No. 3,505,413 describes the preparation of HNS by the reaction of 2,4,6-trinitrotoluene (TNT) with sodium hypochlorite. The yield of HNS obtained by this method ranged up to about 35% after purification and washing. British patent application No. 250,1/76 discloses the preparation of HNS from TNT by a process which is similar to that disclosed in the '413 patent, but which differs by the addition of a nitrogenous base to the reaction mixture at least 0.5 minutes after the start of the reaction. The British Applicants state that the presence of the nitrogenous base increases the yield of HNS to between 45 and 50% of theoretical, by contrast with the yields of the prior art process which ranged from 30 to 35%.
Earlier investigations of the reaction of TNT to form HNS, by Shipp and Kaplan, reported in the Journal of Organic Chemistry, Volume 31, Page 857 (1966), dealt separately with the conversion of 2,4,6-trinitrobenzyl chloride to HNS by reaction with aqueous sodium hydroxide which is present in the sodium hypochlorite solution during its reaction with TNT. For example, with a mole ratio of 1:1.0 of the benzyl chloride to hydroxide, the crude HNS yield was found to be 50%. Likewise, they found that the oxidation of TNT with the hypochlorite resulted in a 42% crude yield of HNS. The crude yields mentioned herein, are significant in that the actual yields of HNS are reduced after the crude products are washed with acetone to remove coprecipitated by-product impurities. Therefore, one of the objects of researchers in the art has been to increase the yield of purified HNS available.
Shipp and Kaplan, in the above-mentioned article isolated the benzyl chloride as an intermediate in the conversion of TNT to HNS. The British Applicants dealt directly with the conversion of TNT, and did not deal with the isolated benzyl chloride. Moreover, the method of the British application contemplates the inclusion of the nitrogenous base together with the excess hypochlorite which is alkaline because of the presence of excess sodium hydroxide.